1. Field of the Invention
The present invention relates to a method of removing metal wires from a tire using dielectric heating, a method of collecting the metal wires and rubber part of the tire, and a method of reusing the tire used in these methods. More specifically, the present invention relates to a method in which the metal wires in a tire are heated using electromagnetic induction, whereby the characteristic of the rubber of the part contacting the metal wires alters to separate the metal wires and rubber part, and thus the metal wires arranged in the tire are separated, collected, and reused. In particular, the present invention relates to a technique for recycling an automobile tire.
2. Description of the Related Art
Although the recycling rate for used automobile tires is much higher than that of other industrial products, the amount of discarded tires continues to increase from year to year, creating an increasingly serious social problem. Among the most sophisticated methods of reusing used tires are a method in which new rubber is adhered to the worn-down parts of a used tire so that the tire can be reused, and a method in which a used tire is cut or shredded into small pieces and used as a mat, pavement material, reclaimed rubber, footwear, and so on. As shown in FIG. 1, however, in almost all cases steel wires 4 are arranged within and incorporated into a bead portion 1 and a tread portion 3 of the tire. Since it is difficult to remove these steel wires cheaply using current technology, the tire cannot be cut or shredded into small pieces. Accordingly, only a sidewall part 2 in which no steel wires are incorporated can be cut or shredded and reused. Further, the sidewall portion constitutes less than 30% of the entire tire. The parts incorporated with steel wires, or in other words the remaining 70%, are used as fuel for cement firing or metal smelting, for example.
However, when used tires are used as fuel, a desulfurizer is required, and furthermore, the burned steel wires cause a large increase in the amount of ash, which is a problem in terms of industrial waste processing. Moreover, in terms of demand, there is a limit to the amount of used tires that can be used as fuel.
When the parts of a tire incorporated with steel wires are cut, shearing is performed using only a cutter, but when soft rubber and tough steel wires must be severed simultaneously, problems arise in that the life of the cutter is shortened, and in that it is technically difficult to sever anything with a magnitude of fifteen square centimeters or less. It goes without saying that if the steel wire-incorporated parts serving as fuel could also be cut into small pieces, combustion efficiency would rise, and benefits would be gained regarding transportation.
Hence if the steel wire in a used tire could be removed, the field of recycling applications could be extended beyond fuel, the use of used tires as fuel would increase in value, and benefits would be gained regarding transportation and storage. Further, if the metal wires could be collected, they could also be recycled into metal.
In light of this situation, the present inventors considered the background art described above and performed various investigations with the object of developing a new method of removing metal wires in which the steel wires in a used tire can be separated and collected efficiently and by a simple operation. As a result of these investigations, it was discovered that by heating the metal wires in the tire using induction heating, the rubber of the part which contacts the metal wires is decomposed and gasified, whereby the metal wires and rubber part can be easily separated and collected. Thus the present invention reached completion.